High-responsivity fiber-optic flexural disk accelerometers

This paper presents performance measurements of fiber-optic flexural disk accelerometers. The flexural disk acts as a mass-spring element to which the fiber is bonded, such that an acceleration causes a strain to be imposed on the fiber which is measured interferometrically, Simple analytical models have been written to calculate the responsivity and resonant frequency of disks under various boundary conditions and the results of the models have been shown to be in good agreement with the measured responsivity for the case of moderately thick disks. Six optical fiber accelerometers based on flexural disks of different thickness and supports have been demonstrated to exhibit a responsivity in the range from 28 to 39 dB re 1 rad/g with a resonant frequency between 2.4 kHz to greater than 5 kHz, respectively. Of the designs considered, the centrally supported dish is shown to give the highest combination of responsivity and bandwidth. A centrally supported disk has been demonstrated to exhibit a flat response up to 2 kHz and a responsivity of 37 dB re I rad/g which when combined with an interferometric phase resolution of 6 mu rad/root Hz, would give a minimum detectable acceleration of 84 ng/root Hz. We have attempted to cover all aspects of the sensor design including responsivity, bandwidth, cross-responsivity, phase response and size and find that a complicated compromise between all of these design parameters is required to achieve the optimum performance.